An ink jet recording apparatus has been known, which has a recording head for discharging ink as droplets onto a recording medium to print an image. The ink jet recording apparatus is provided with at least an ink tank containing an ink, to supply the ink from the ink tank to the recording head. In a serial ink jet recording apparatus, a recording head is mounted to a carriage that moves back and forth in a main scanning direction, a widthwise direction of a recording paper. Each time the carriage makes one lap, the recording head records a line of image, and then the recording paper is fed in a sub scanning direction orthogonal to the main scanning direction by an amount corresponding to the image line. Thus, an image frame is printed serially line after line.
Because the ink is a consumable material, the ink tank is often formed as a cartridge that is removably attached to the ink jet recording apparatus, so as to make it easy to refill the ink jet recording apparatus with the ink. Such a cartridge type ink tank, hereinafter called the ink cartridge, is attached to the carriage in association with the recording head.
The ink jet recording apparatus has an ink supply path that leads to the recording head. As the ink cartridge is attached to the carriage, an ink outlet of the ink cartridge is connected to one end of the ink supply path. Thus, the ink cartridge can supply the ink to the recording head. As an example, the ink supply path is constituted of a hollow ink supply needle. The ink outlet is provided with a filter made of a porous material like sponge, and one end of the ink supply needle is stuck into the filter.
As the ink cartridge is detached from the carriage, the ink supply needle is pulled out of the filter. At that time, dusts are likely to enter inside the ink cartridge through the ink outlet. To prevent the entrance of dusts, an ink cartridge as disclosed for example in Japanese Laid-open Patent Application No. Hei 8-183185, is provided with a valve that is pushed by the ink supply needle to open the ink outlet. As the ink cartridge is detached and the ink supply needle is removed from the ink outlet, the valve closes the ink outlet. In addition to that, the ink cartridge of this prior art sections an ink chamber into a main chamber and a sub chamber, wherein the sub chamber directly leads to the ink outlet, and a filter is disposed between the sub chamber and the main chamber. Thereby, dusts are surely blocked from the main chamber.
However, because the ink cartridge should be mounted on the carriage to move with the carriage, the ink cartridge is expected to be as small as possible. Also, because the ink cartridge is a consumable product that should be changed after the contained ink is used up, the structure of the ink cartridge is desired to be as simple as possible to save the cost. Since the ink cartridge of the above mentioned prior art is provided with the valve, and is sectioned into two chambers, it is difficult to make it small and simple.
An easy way to prevent the entrance of dusts into the ink cartridge is disposing a filter of finer texture in the ink outlet. But the finer is the filter, the larger pressure loss through the filter becomes, which results in requiring the stronger sucking power of the recording head for sucking the ink out of the ink cartridge. Proving the recording head with the stronger sucking power will increase the cost of the recording head itself.